DemoUseSessionMessageHost now reads ShellProgress / NcDiagnosticProgress /
StepDiagnosticProgress (severity + id + notification, with the per-kind NC-line
/ step anchors). Drop DemoUseSessionMessageHost2 — its premise (reading
MachiningStep objects out of the mixed message list) dissolves under the
partition; step-data demos live in ShowStepPresent and SessionStepBuilt.
DemoUseMachiningProject's abnormal-message log now subscribes the three sinks'
MessageAdded events (shell via the OnShellMessageAdded app-lifetime bridge).
Part of MixedProgress0 retirement (migration P6). Build x64 green.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
